Abstract: Based on the field tests of vacuum well-point dewatering, the evolutions of groundwater level and the variations of the water flow in silt ground layer are studied under combined gravitational and vacuum negative pressure, which include both the cases of a single well-point and a single row well-point. Test results show that, for the condition of a single well, the declining depths of groundwater level increase with the increase of vacuum negative pressure and the depth of drainage well, and the declines of groundwater level at the points away from the drainage well will be more obvious. For the condition of a single row well-point, with the increase of the depth and space of drainage wells, the declines of groundwater level are also very apparent whether along the direction of well-point arrange or in the perpendicular direction of well-point arrange; and the former is more obvious. On the other hand, the declining ratio of groundwater level has an increasing trend after several repeated dewatering processes. Besides, the vacuum pressure in the mouth of a well is lower than it in the water outlet of vacuum pump with a loss of approximately 12.5%, which indicates that the length of the pipeline of water outlet should be considered in the design of vacuum well-point dewatering in practice.

Key words: single well-point, single row well-point, groundwater level, silt foundation, vacuum negative pressure